Alpha-olefins such as butene are desirable substances in the chemical industry. Due to the presence of the terminal double bond, they can be converted into a number of other valuable compounds. For example, butene can be converted to compounds such as butanol, butadiene, and butanone. In polymerisation reactions it can be used as monomer or co-monomer and is particularly valuable in the production of plastics. For example, it can be used as a co-monomer with ethylene for the production of high strength and high stress crack resistant polyethylenes. One route to the preparation of butene is the cracking of higher petrochemical fractions containing more than 4 carbon atoms. Another route to the preparation of butene, which has for a long time been the subject of intense research, is via the dimerization of ethylene (ethene). An aim of the catalytic dimerization of ethylene into 1-butene was producing higher chain polymers via the growth reaction of the organoaluminum compounds. The industrial synthesis of 1-butene can be achieved using nickel or titanium catalysts such as Alphabutol™ (Handbook of Petroleum Processing, Edited by D. S. J. Jones, P. R. Pujadó; Springer Science 2008; Forestière et al., Oil & Gas Science and Technology—Rev. IFP (2009); 64(6):649-667). The Alphabutol™ process is also known as BUCAT. The catalytic activity of Alphabutol™ can be low, at roughly 1 kg of product per gram of titanium. Polymer formation and lengthy initial induction period are major drawbacks for the commercial Alphabutol™ system.
Thus, a demand still remains in the art for improved processes for the preparation of α-olefins such as butene from alkenes such as ethene, especially for processes with one or more of long catalyst lifetimes, high specificity, short initiation times (induction periods), and reduced polymer formation.